The big news from the solar scene is the proposition that coronal mass ejections (CMEs), not solar flares, are the prime culprits responsible for big geomagnetic storms. The proposition has opponents, but by mid-1994 the arguments supporting it were more fully developed and exposed, as Dave Webb reports in his `Coronal mass ejections: The key to major interplanetary and geomagnetic disturbances.' In a related item, the shock waves of CMEs are now thought to be responsible for major solar energetic particle events (SEPs), the main solar radiation hazard. Like geomagnetic storms, SEPs had been attributed to solar flares. The new view is required to explain data on isotopic abundances of helium and heavy ions, as Don Reams explains in his `Solar energetic particles: A paradigm shift.'
News from the heliosphere is dominated by the Ulysses over-the-pole mission, which has begun to fill in major pieces of the heliospheric map. Meanwhile, the indefatigable Pioneer and Voyager spacecraft continue their valuable reconnaissance of the outer heliosphere. Marcia Neugebauer's `Charting the heliosphere in three dimensions' describes the main features that have been added to the heliospheric map from all missions as of mid-1994. She emphasizes the average climatological features structured in the basic solar wind parameters of speed, density, temperature, and magnetic field. The weather within that climatology, heliospherists tell us, comprises corotating interaction regions and transients, caused mainly by the heliospheric passages of CMEs. Jack Gosling's `Solar wind corotating interaction regions: The third dimension' reports that Ulysses has completed the first high-latitude survey of these characteristic, time dependent features. To represent the other kind of heliospheric weather, transients, Dave McComas describes how they operate to keep the solar magnetic flux at a nearly constant level, in his `Tongues, bottles, and disconnected loops: The opening and closing of the interplanetary magnetic field.' Like tropospheric weather, heliospheric weather has its turbulence, which governs the transport of energy from the macroscale to the dissipation regime and, for the heliosphere, which governs energetic particle and cosmic ray transports. In `Unquiet on any front: Anisotropic turbulence in the solar wind,' Bill Matthaeus, John Bieber, and G. Zank report that the past four years have seen the `uncovering' of a previously under-appreciated component to the turbulence that could account for more than half the variance. It might be thought of as `randomly distributed bundles of spaghetti [magnetic flux tubes] with varying cross sections, aligned with the mean magnetic field.'
Also like the troposphere, the heliosphere has its chemistry, which informs on the solar sources of the solar wind and on the presence---long-predicted but now detected---of interstellar `pollutants.' Keith Ogilvie and Michael Coplan's `Solar wind composition' summarizes in useful tables the diagnostic power of trace-element chemistry applied to the solar wind with space-borne instruments, whose increasing sophistication has culminated in time-of-flight mass spectrometers. Phil Isenberg continues the story with `Interstellar pickup ions: Not just theory anymore,' which recounts how time-of-flight mass spectrometers have finally enabled the detection of the interstellar medium in situ. Interstellar neutrals permeate the heliosphere, become ionized by solar photons, get post-accelerated by the solar wind (``picked up'' in the parlance of the trade), and detected in the low-background environment of a time-of-flight system---the whole thing operates like an ionizing mass spectrometer. The measurement of interstellar particles in situ adds one more lane---others being cosmic ray measurements and measurements of luminosity variations of solar-like stars---to the bridge connecting space physics to astrophysics.